1. Field of the Invention
The present invention is related to a method for dispatching of service requests in redundant storage virtualization subsystems.
2. Description of the Prior Art
One important feature that characterizes Storage Virtualization Subsystems (SVSs) is the ability to configure, manage and/or monitor the subsystem by a host entity. To accomplish this, the Storage Virtualization Controller(s) (SVC(s)) in the system implement protocols that communicate configuration, management and monitoring information between at least one SVC in the SVS and the host entity. These protocols typically support such communication to take place over multiple types of physical media, such as RS-232, LAN, host-side IO device interconnect, etc. In the case of a SVS that consists of redundantly configured SVCs, such exchanges can traditionally only take place between one of the SVCs in the redundant combination, typically referred to as the Primary SVC, and the host entity, for only the Primary SVC is equipped to receive, dispatch and/or execute configuration, management and monitoring requests (hereafter referred to as Service requests). This is an important architectural characteristic that is adopted in an effort to avoid possible conflicts that may arise if two or more SVCs in the redundant combination attempt to concurrently Service such requests.
As mentioned above, the SVC(s) in a SVS typically implement protocols that communicate configuration, management and monitoring information (hereafter referred to as Service information) between one of the SVCs in the SVS and the host entity. If the SVS consists of a set of redundantly configured SVCs, then, traditionally, such exchanges are conducted entirely between the Primary SVC in the redundant combination and the host entity. The other SVC(s) in the redundant combination, referred to hereafter as Secondary SVCs, are not directly involved with the exchanges and the servicing of Service requests that are conveyed. While this kind of a limitation, when the host entity can always access any SVC in the redundant combination, does not necessarily introduce additional operational limitations, there may be configurations in which the connection from the host entity to one or more of the SVCs in the redundant combination does not exist or situations in which breaks or malfunctions in connections cause the host entity to lose the ability to communicate with one or more SVCs in the redundant combination. This, in turn, gives rise to the possibility that the host entity may not have to begin with (due to configurational peculiarities) or have and then lose (due to connection break or malfunction) the ability to convey Service requests to the SVS. In certain applications in which the processing of Service requests is critical to the proper functionality of the system, such lack or loss of ability to convey Service requests could well be unacceptable.
Accordingly, there is a need for a method to solve the above-mentioned problems of the existing technologies.